1. Field of the Invention
This invention concerns a laminated pane, comprising an adhesive film disposed in between at least one glass sheet and at least one sheet of plastics material. The adhesive film has the characteristic of greater adhesion to the glass sheet than to the sheet of plastic material. The laminates are especially useful as safety panes in buildings and vehicles.
2. Discussion of the Background
Laminated panes for buildings or transportation vehicles are generally constructed of two glass sheets, between which is placed a sheet of thermoplastics polymer. Commonly, the thermoplastic polymer comprises polyvinyl butyral (PVB).
PVB is used as intermediate sheet because it has a high tension modulus, it exhibits considerable elongation at rupture, and because it is an efficient energy-absorber. Therefore, it can effectively withstand impact. At the same time, PVB has a relatively high adhesion to glass. Therefore, if the glass shatters or splinters as a result of impact or breakage of the pane, the broken glass has a tendency to be retained by the PVB.
PVB, however, is not entirely satisfactory because it is considered relatively expensive. Furthermore, properties other than energy absorption and adhesion to the glass are often desired, depending on the application. The final laminate is therefore often the result of a compromise between various properties.
As an example, U.S. Pat. No. 4,600,627, teaches a laminated pane including a plurality of sheets of plastics material between two glass substrates. The plurality of sheets comprise a central sheet of a first plastics material, such as polyester or polyvinyl chloride (PVC), disposed between two sheets made of a material which serves to adhere the intermediate sheet and the glass sheets. As exemplified in the reference, these two sheets may be based upon a copolymer of ethylene and of vinyl acetate (EVA) and may have a thickness of around 0.2 mm. This structure has several problems, however. In particular, the sheets of EVA do not have adequate adhesive properties and, more importantly, the laminated pane cannot withstand extremes of temperature.